Electrical calculator

Volts to Joules Calculator

Relate voltage, charge, or capacitance to energy in joules for electrostatic and capacitor examples. Runs locally in your browser. Try it free.

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Enter values to calculate.

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Formula—

Trust summary Engine tested · Source checked · 12/12 tests · Production surface contract 4/4 · v1.2.0

Input interpretation: Enter values to calculate.
Result: —
Model: Energy from voltage and charge, or voltage from energy and charge (coulombs or elementary charges).
Scope: Electrostatic potential energy relation; Q is the charge moved through V
Verification: Engine tested · 12/12 tests · Production surface contract 4/4 · Source checked · v1.2.0
Named expert review: Optional · Not performed
Sources: SI definition of the volt — 1 V = 1 J/C (energy per unit charge)
NIST Guide to the SI (SP 811) — Joule, volt, coulomb relationships
CODATA elementary charge — e ≈ 1.602176565×10⁻¹⁹ C (page constant)
Sources
Evidence: 12 golden · Production surface contract 4/4 · Artifact integrity PASS
Production: Embedded snapshot: STALE · Last attested schema matched 1.2.0 snapshot / local build · Semantic contract ✓ · Last attestation PASS · current evidence changed · re-attestation required · Public/cache ✓ · Origin ✓ · Live production status STALE (1 capability; 163 remain CURRENT) @ 2026-09-19T00:00:17.039Z
Semantic contract: PASS

Formulas

Core equations used by this calculator.

Volts → joulesE(J) = V(V) × Q(C)

Joules → voltsV(V) = E(J) ÷ Q(C)

Volts → joules (elementary)E(J) = V × Q(e) × 1.602176565×10⁻¹⁹

Joules → volts (elementary)V = E ÷ (Q(e) × 1.602176565×10⁻¹⁹)

iOne volt is one joule per coulomb. Enter charge in coulombs (1 mC = 0.001 C, 1 μC = 10⁻⁶ C). For one elementary charge at 1 V, E ≈ 1.602×10⁻¹⁹ J = 1 eV.

How to use

Choose direction

V → J for energy from voltage and charge, or J → V for voltage from energy and charge. Use (e) tabs for elementary charge.

Enter voltage (or energy) and charge

Charge must be in coulombs on the C tabs, or count of elementary charges on the e tabs.

Read joules or volts

The result updates as you type. Tiny particle-scale values show in scientific notation.

Example calculations

Common configurations with formula and result.

12 V · 5 C

Common default check

12 × 5

60 J

12 V · 1 C

One coulomb of charge

12 × 1

12 J

120 V · 1 C

Mains-scale potential, 1 C

120 × 1

120 J

Joules → volts

60 J · 5 C

60 ÷ 5

12 V

Single electron · 1 V

Q = 1 e

1 × 1 × 1.602×10⁻¹⁹

≈ 1.602×10⁻¹⁹ J (1 eV)

Volts → joules at Q = 1 C

Common values at a glance.

Voltage	Charge	Energy
1 V	1 C	1 J
12 V	1 C	12 J
12 V	5 C	60 J
120 V	1 C	120 J
1000 V	1 C	1000 J
50,000 V	1 C	50,000 J

i At Q = 1 C, joules equal the numeric volt value. Halve the charge and energy halves. Convert charge prefixes first: 2 mC = 0.002 C.

Volts to Joules calculator specification

Version 1.2.0 · Engine tested

Calculation status

Engine tested 12/12 tests · Production surface contract 4/4
Named expert review Not performed
Calculation version 1.2.0

Review policy · Evidence

Definition: Voltage is energy per unit charge: 1 V = 1 J/C. Energy in joules is therefore E = V × Q, where Q is charge in coulombs. To find voltage from energy, use V = E ÷ Q. You cannot convert volts to joules without a charge (or equivalent). This tool also supports charge counted in elementary charges e ≈ 1.602×10⁻¹⁹ C.
What it calculates: Energy from voltage and charge, or voltage from energy and charge (coulombs or elementary charges).
Inputs: Voltage (V) and charge (C or e) → joules
Energy (J) and charge (C or e) → volts
Outputs: Energy in J, or voltage in V
Formula: E=V·Q; V=E/Q; with Q(e)·e for elementary charge
Assumptions: Electrostatic potential energy relation; Q is the charge moved through V
Units: V, C → J
J, C → V
Boundary conditions: V→J (product): zero V or Q → 0 J
J→V (quotient): Q = 0 → 0 V — soft
Elementary path uses e = 1.602176565×10⁻¹⁹ C (scale-product / scale-quotient)
Zero energy on J→V → 0 V
Example: 12 V × 5 C = 60 J
Validation cases: 12 published on this page · 12/12 tests · Production surface contract 4/4 · View evidence
12 V, 5 C → 60 J
60 J, 5 C → V → 12 V
1 V, 1 e → ≈ 1.602176565×10⁻¹⁹ J
12 V, 1 C → 12 J
24 V, 5 C (2× V) → 120 J (linear in V)
12 V, 10 C (2× Q) → 120 J (linear in Q)
0 V, 5 C → 0 J
12 V, 0 C → 0 J
60 J, 0 C → V → 0 V (soft: zero Q → 0)
0 J, 5 C → V → 0 V
1.602176565×10⁻¹⁹ J, 1 e → V → 1 V
12 V → 60 J → V round-trip at 5 C → 12 V
Sources: SI definition of the volt — 1 V = 1 J/C (energy per unit charge)
Supports: E = V × Q; V = E / Q
NIST Guide to the SI (SP 811) — Joule, volt, coulomb relationships
Supports: Coherent SI units for electrostatic energy
CODATA elementary charge — e ≈ 1.602176565×10⁻¹⁹ C (page constant)
Supports: V→J (e) and J→V (e) scale factors
Calculation version: 1.2.0

Background

Interpretation and common distinctions.

Convert volts and charge to joules, or joules and charge back to volts.

E((J)) = V((V)) × Q((C)) V((V)) = (E((J)))/(Q((C)))

Default example: 12 V × 5 C = 60 J.

Modes

Tab	Formula	Use when
V → J	E = V × Q	Charge in coulombs
J → V	V = E ÷ Q	Find potential from energy and charge
V → J (e)	E = V × Q((e)) × e	Particle / atomic charge count
J → V (e)	V = E ÷ (Q((e)) × e)	Same, reverse

Elementary charge: e ≈ 1.602176565×10⁻¹⁹ C.

Why charge is required

A volt is energy per unit charge (1 V = 1 J/C). Joules are energy. Without knowing how much charge moves through the potential, voltage alone does not fix an energy value.

Related but different path: E = P × t (watts × seconds) — use watts to joules when you know power and time instead of V and Q.

Other calculators in this family: Amps to kW Calculator, Amps to VA Calculator, Amps to Volts Calculator, Electric Power Calculator, Energy Consumption Calculator, Energy Cost Calculator, eV to Volts Calculator, kVA to Amps Calculator . Explore all Power & Energy.

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Frequently asked questions

Key distinctions behind the calculation.

How do I convert volts to joules?

Multiply voltage by charge: E (J) = V (V) × Q (C). Voltage alone is not energy — you need Q (or an equivalent such as current × time).

How do I convert joules to volts?

Divide energy by charge: V = E ÷ Q. One volt equals one joule per coulomb.

Why can't I convert V to J without charge?

Volts measure potential (energy per charge). Joules measure energy. Relating them always needs how much charge moves through that potential.

What charge units can I use?

Enter coulombs on the C tabs. Convert first if needed: 1 mC = 0.001 C, 1 μC = 10⁻⁶ C, 1 nC = 10⁻⁹ C. Use the (e) tabs for a count of elementary charges.

How is this related to electronvolts?

1 eV is the energy of one elementary charge through 1 V, about 1.602×10⁻¹⁹ J. For particle energies in eV vs volts, use the eV to volts calculator.

Is this the same as watts × time?

No. Watts × seconds also gives joules (E = P × t), but that path uses power and time, not voltage and charge. Use watts to joules for that case.

What if charge is zero?

J → V is undefined when Q = 0 (division by zero). V → J with Q = 0 correctly gives 0 J.